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Number of odd nonprime differences of 2 (twin odd nonprimes) below 10^n.
1

%I #18 Apr 29 2024 09:08:58

%S 0,9,200,2748,32041,351174,3729823,38917403,401729439,4117307658,

%T 41988266423,426654761185,4323703591195,43725896820062,

%U 441488068396967,4451827513629449,44843834524044694,451328767313095717

%N Number of odd nonprime differences of 2 (twin odd nonprimes) below 10^n.

%C Count twin odd nonprimes below 10^n.

%F a(n) = 10^n/2 - 2*A006880(n) + A007508(n) + 1. - _Max Alekseyev_, May 11 2005

%e a(2) = 9 because below 100 there are 9 twin odd nonprimes, e.g., 27 - 25 = 2.

%Y Cf. A093683, A006880, A007508.

%K nonn,more

%O 1,2

%A _Enoch Haga_, Apr 10 2004

%E More terms from _Max Alekseyev_, May 11 2005

%E a(16) corrected and a(17)-a(18) added using the data at A006880 and A007508 by _Amiram Eldar_, Apr 29 2024